<template>
  <div class="music-list">
    <div class="back" @click="back">
      <li class="icon-back"></li>
    </div>
    <h1 class="title" v-html="title"></h1>
    <div class="bg-image" :style="bgStyle" ref="bgImage">
      <div class="play-wrapper">
        <div class="play" v-show="songs.length" ref="playBtn">
          <i class="icon-play"></i>
          <span class="text">随机播放全部</span>
        </div>
      </div>
      <div class="filter" ref="filter"></div>
    </div>
    <div class="bg-layer" ref="layer"></div>
    <scroll @scroll="scroll" :probe-type="probeType" :listen-scroll="listenScroll" :data="songs" class="list" ref="list">
      <div class="song-list-wrapper">
        <song-list @select="selectItem" :songs="songs"></song-list>
      </div>
      <div class="loading-container" v-show="!songs.length"></div>
        <loading></loading>
    </scroll>
  </div>
</template>

<script type="text/ecmascript-6">
import Scroll from 'base/scroll/scroll'
import SongList from 'base/song-list/song-list'
import {prefixStyle} from 'common/js/dom'
import Loading from 'base/loading/loading'
import {mapActions} from 'vuex'

const  RESERVED_HEIGHT=40
const  transform=prefixStyle('transform')
const  backdrop=prefixStyle('backdrop-filter')

  export default {
    props: {
      bgImage: {
        type: String,
        default: ''
      },
      songs: {
        type: Array,
        default: []
      },
      title: {
        type: String,
        default: ''
      }
    },
    data(){
      return{
        scrollY:0
      }
    },
    computed:{
      bgStyle(){
        return `background-image:url(${this.bgImage})`
      }
    },
    created(){
      this.probeType=3
      this.listenScroll=true
    },
    mounted(){
      this.imageHeight=this.$refs.bgImage.clientHeight
      this.minTranslateY=-this.imageHeight+RESERVED_HEIGHT
      this.$refs.list.$el.style.top=`${this.imageHeight}px`
    },
    methods:{
      scroll(pos){
        this.scrollY=pos.y
      },
      back(){
        this.$router.back()
      },
      selectItem(item,index){
        this.selectPlay({
          list: this.songs,
          index
        })
      },
      ...mapActions([
        'selectPlay'
      ])
    },
    watch:{
      scrollY(newY){
        let translateY=Math.max(this.minTranslateY,newY)
        let zIndex=0
        let scale=1
        let blur=0
        this.$refs.layer.style[transform]=`translate3d(0,${translateY}px,0)`
        const percent=Math.abs(newY/this.imageHeight)
        if(newY>0){
          scale=1+percent
          zIndex=10
        }else {
          blur=Math.min(20*percent,20)
        }
        this.$refs.filter.style[backdrop]=`blur(${blur}px)`

        if(newY<this.minTranslateY){
          zIndex=10
          this.$refs.bgImage.style.paddingTop=0
          this.$refs.bgImage.style.height=`${RESERVED_HEIGHT}px`
          this.$refs.playBtn.style.display='none'
        }else{
          this.$refs.bgImage.style.paddingTop='70%'
          this.$refs.bgImage.style.height=0
          this.$refs.playBtn.style.display=''
        }
        this.$refs.bgImage.style.zIndex=zIndex
        this.$refs.bgImage.style[transform]=`scale(${scale})`

      }
    },
    components:{
      Scroll,
      SongList,
      Loading
    }
  }
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"
  @import "~common/stylus/mixin"

  .music-list
    position: fixed
    z-index: 100
    top: 0
    left: 0
    bottom: 0
    right: 0
    background: $color-background
    .back
      position absolute
      top: 0
      left: 6px
      z-index: 50
      .icon-back
        display: block
        padding: 10px
        font-size: $font-size-large-x
        color: $color-theme
    .title
      position: absolute
      top: 0
      left: 10%
      z-index: 40
      width: 80%
      no-wrap()
      text-align: center
      line-height: 40px
      font-size: $font-size-large
      color: $color-text
    .bg-image
      position: relative
      width: 100%
      height: 0
      padding-top: 70%
      transform-origin: top
      background-size: cover
      .play-wrapper
        position: absolute
        bottom: 20px
        z-index: 50
        width: 100%
        .play
          box-sizing: border-box
          width: 135px
          padding: 7px 0
          margin: 0 auto
          text-align: center
          border: 1px solid $color-theme
          color: $color-theme
          border-radius: 100px
          font-size: 0
          .icon-play
            display: inline-block
            vertical-align: middle
            margin-right: 6px
            font-size: $font-size-medium-x
          .text
            display: inline-block
            vertical-align: middle
            font-size: $font-size-small
      .filter
        position: absolute
        top: 0
        left: 0
        width: 100%
        height: 100%
        background: rgba(7, 17, 27, 0.4)
    .bg-layer
      position: relative
      height: 100%
      background: $color-background
    .list
      position: fixed
      top: 0
      bottom: 0
      width: 100%
      background: $color-background
      .song-list-wrapper
        padding: 20px 30px
      .loading-container
        position: absolute
        width: 100%
        top: 50%
        transform: translateY(-50%)
</style>
